7 Drugs You're Taking That Might Be Wrecking Your Workout

If your usual sweat session feels unusually tough, your medication may be to blame. Both prescription and over-the-counter drugs can cause a host of side effects—some of which might not be apparent until you hit the weight room or lace up your sneakers.

And new meds aren’t the only ones that can cause problems.

Though less common, it’s possible for your body to react differently to a medication over time—which means you could suddenly start feeling the effects of a drug that you’ve been taking for a while, says Dave Dixon, Pharm.D, an associate professor at Virginia Commonwealth University’s School of Pharmacy.

Here’s a look at 7 common culprits, how they can wreck your workout, and what you can do to get back on track. (Need a workout reboot? Try The 21-Day MetaShred from Men's Health—you'll burn fat and build lean muscle.)

Workout Wrecker: Decongestants

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Popping a Sudafed before you exercise could leave you feeling like you’re working out way harder than you actually are. Decongestants fight nasal inflammation and swelling by constricting blood vessels, which can raise your heart rate and blood pressure, says Dr. Goudreau.

So when you add intense physical activity to the mix, you could end up getting tired out faster since your body is already pushing hard.

If you’re young and generally healthy and you’re suffering from a cold, it’s still fine to exercise as long as you feel up to it. Or, just wait until the meds wear off—usually within 4 to 6 hours.

But avoid exercising while taking decongestants if you have heart disease or high blood pressure or are over 40, Dr. Goudreau says. (Being older ups the odds that you have an undiagnosed heart problem, and the meds combined with the exercise could stress your heart. So it’s better to play it safe.)

Workout wrecker: Sleeping pills

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Sleeping pills work by mimicking neurotransmitters that induce drowsiness to help you snooze more soundly, says Dixon. That wooziness can last through the next morning though, making A.M. workouts feel tougher.

Sleeping pills can also affect the part of your brain responsible for helping you balance, leaving you feeling dizzy and uncoordinated. That could put you at risk for falling or dropping a weight and hurting yourself.

The effects are common with sleeping pills like Lunesta, Ambien, and Intermezzo, which are designed to help you sleep longer (as opposed to short-acting sleeping pills like Sonata, which are geared towards helping you doze off faster).

“They’re more likely to cause a ‘daytime hangover,’ Dixon says. In that case, “waiting until later in the day to exercise might be better than an early morning workout.” The effects usually wear off by mid-morning.

Workout Wrecker: Statins

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The exact mechanism is unclear, but cholesterol-lowering drugs are known for causing muscle aches and pains, Dixon says. That can make you more prone to discomfort during a workout, and leave you more sore afterwards. That might make you less likely to push yourself as hard as normal.

The problem usually starts within a few days to a few weeks after starting the meds.

And you’ll know it’s probably from your statin (as opposed to an injury) if your symptoms occur in major muscle groups (like the legs, thighs, and back) on both sides of your body and persist for a couple of weeks instead of getting better, Dixon explains.

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If you notice discomfort, talk to your doctor. “Reducing the statin dose or changing to a different statin may alleviate muscle aches and pains,” Dixon says.

Never stop taking a statin abruptly or without your doctor’s consent, since doing so could increase your risk for a heart attack or stroke.

Workout Wrecker: Antihistamines

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Antihistamines like Benadryl work by blocking brain receptors for histamines—immune system chemicals that trigger allergy symptoms. That relieves your itching and sneezing, but it also has a sedative effect on the brain that can sink in within 30 minutes, says Jeff Goudreau, M.D, an internist at Texas Health Hospital Dallas.

As a result, you could feel drowsy. You might be more likely to drag through your workout, and workouts that call for more focus—like HIIT circuits or multi-move exercises—could be tougher. Your normal load might feel heavier than usual, too.

If Benadryl zaps your energy, you could try a different class of allergy meds, like Claritin, Allegra, or Zyrtec, which some people find less sedating. Or, switch to a nasal steroid, says Dr. Goudreau. It’ll help ease your symptoms without the sleep-inducing side effects.

Workout Wrecker: Muscle relaxers

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Drugs like Amrix and Zanaflex work by blocking neurotransmitters that transmit signals from the brain to the body that control involuntary movements. That can help ease painful muscle spasms, but it can also cause side effects like dry mouth and blurred vision, explains Dixon.

As a result, you’ll feel more dehydrated, which could make it harder to push yourself through your workout. Having trouble seeing could also impair your coordination, making you more likely to trip, fall, or drop a weight and get hurt. And since muscle relaxers work quickly, you’ll feel the effects within a few hours of taking them.

You could try taking your meds at night and working out in the morning. The effects will have likely worn off by then, Dixon says.

But depending on the extent of your injury or muscle spasm, it might be better to skip exercise altogether until you’re fully healed, says Dixon. Check with your doctor to figure out what’s best.

Workout Wrecker: Beta blockers

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Hypertension meds called beta blockers work by blocking the effects of adrenaline—the hormone that triggers your body’s fight-or-flight response. That causes your heart rate to slow down and your blood pressure to drop.

As a result, the meds can leave you feeling weak or tired, which could slow down your performance, Dr. Goudreau says. Feeling weaker could also cause you to fail your usual lift and leave you injured. They can also make you dizzy, which could mess with your coordination.

Most people take beta blockers for heart disease, abnormal heart rate, or high blood pressure. (They can also be prescribed for migraines and anxiety.)

But it’s still safe to exercise on them. “Physical activity is the best medicine for patients on beta blockers, because it will invariably help their high blood pressure or heart disease,” says Dr. Goudreau.

Just don’t push yourself too hard. Stick to moderate exercise where you’re still able to talk without much difficulty (especially when you first start on the meds, to see how your body reacts to them). If you usually go by your target heart rate, ask your doctor about the right number to aim for, recommends the American Heart Association. (You might not be able to reach the target heart rate you had before taking beta blockers, since the meds slow everything down.)

Workout Wrecker: Antidepressants

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Some selective serotonin reuptake inhibitors (SSRIs), like Paxil, Prozac, and Zoloft work by preventing the reabsorption of the neurotransmitter serotonin, which can have a sedative effect. That can leave you drowsy and fatigued, so you have less energy to work out.

But the problem won’t happen right away. Since antidepressants usually take a few weeks to kick in, it might take that long before you start to notice the effects, Dixon says.

“Exercise is really important in patients with depression because it’s been shown to improve mood and general well-being,” Dixon says. “It may also be difficult to determine if the antidepressant is affecting your workout or that your depression simply isn’t well-controlled.”

So bring up the issue with your doctor. He may suggest adjusting your dosage or switching you to another antidepressant.

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